Apparatus and method for tracking contour of moving object, and apparatus and method for analyzing myocardial motion

ABSTRACT

A moving object contour tracking apparatus includes a contour tracking section for performing, by taking an initial contour of the moving object in a predetermined image slice as a starting contour, contour tracking in a first time direction to acquire a first contour of the moving object and contour tracking in a second time direction to acquire a second contour of the moving object in each image slice; a contour comparison section for calculating, in the predetermined image slice, a similarity between the first contour and the initial contour and a similarity between the second contour and the initial contour; and a contour correction section for taking the contours in the image slices that are acquired in a contour tracking direction corresponding to the greater one of the two similarities as the contours of the moving object in the respective image slices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 13/553,308 filed Jul. 19, 2012,and claims the benefit of priority under 35 U.S.C. §119 from ChinesePatent Application No. 201110209868.9 filed Jul. 19, 2011, the entirecontents of each of which are incorporated herein by reference.

FIELD

The present invention relates to the field of computer vision and moreparticularly, to a apparatus and method for tracking contour of movingobject, and apparatus and method for analyzing myocardial motion.

BACKGROUND

The contour extraction of a moving object, especially of a deformingobject, is a challenge in the field of computer vision. In actualapplications, for example, in the medial field, the contour extractionof an organ or a part of an organ from a three-dimensional image timeseries acquired by a computed tomography (CT) apparatus, a MagneticResonance Imaging (MRI) apparatus, an ultrasonic (UL) apparatus and thelike is beneficial to subsequent measurement on various parameters ofthe organ.

Some conventional moving object contour extraction methods extract thecontour of a moving object separately from each phase, which may lead toan error extraction in a specific phase.

Some other motion tracking based methods which track the contour of amoving object in a motion period of the moving object may produce anerror accumulation, resulting in a significant difference between theacquired contour in the first phase and that in the last phase.

In addition, in the field of cardiology, a nuclear magnetic resonanceimaging technology is typically used to provide a three-dimensionalimage time series (3D+T) of a heart. Doctors are highly interested inrecognizing a ventricle, an endocardium, an epicardium and analyzing themotion of a heart. The contours of the recognized ventricle, endocardiumand epicardium can be used to measure a ventricular blood volume(ejection fraction), the motion of a ventricular wall, a characteristicof wall thickness and the like at different stages of a cardiac cycle.The motion vector of a myocardium can be used to calculate parameters ofthe myocardium, such as strain and strain force. Left ventricle (LV) isof great importance because it pumps oxygenated blood to various issuesof a body from the heart.

There have been developed many medical motion image processingtechniques to quantify myocardial motion, including spot tracking,myocardial tagging, registering and propagation contours with initialcontour of myocardium, and various myocardium segmentation methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood by reference to thefollowing description taken in conjunction with accompanying drawings inwhich identical or like sections are designated with identical or likereference signs designate. The accompanying drawings, together with thedetailed description below, are incorporated into and form a part of thespecification, and serve to further illustrate, by way of example,preferred embodiments of the present invention and to explain theprinciple and advantages of the present invention. In the accompanyingdrawings:

FIG. 1 is a schematic flow chart illustrating a moving object contourtracking method according to an embodiment of the present invention;

FIG. 2 shows an application example of the moving object contourtracking method according to the embodiment of the present invention;

FIG. 3 is a schematic flow chart illustrating a contour tracking stepaccording to an embodiment of the present invention;

FIG. 4 shows examples of a contour region of interest (ROI) and atracking cell;

FIG. 5 is a schematic diagram illustrating a conversion relationshipbetween a Euclidean coordinate system and a polar coordinate system;

FIG. 6 is a schematic flow chart illustrating a method for acquiring aninitial contour of a left ventricle according to an embodiment of thepresent invention;

FIG. 7 shows a schematic flow chart illustrating the acquiring of anendocardial contour of a left ventricle according to an embodiment ofthe present invention;

FIG. 8A shows an example of a gray scale image of an image slice in apolar coordinate system;

FIG. 8B shows an example of a horizontal projection of the gray scaleimage shown in FIG. 8A;

FIG. 9 is a schematic flow chart illustrating the acquiring of aninitial contour of a left ventricle according to another embodiment ofthe present invention;

FIG. 10 is a schematic flow chart illustrating the acquiring of anepicardial contour of a left ventricle according to an embodiment of thepresent invention;

FIG. 11A shows an example of an edge image of an image slice in a polarcoordinate system;

FIG. 11B shows an example of a horizontal projection of the edge imageshown in FIG. 11A;

FIG. 12A shows examples of an endocardial contour and an epicardialcontour acquired in a polar coordinate system;

FIG. 12B shows an example of conversion of the endocardial contour andthe epicardial contour acquired in FIG. 12A into an original imageslice;

FIG. 13 is a schematic flow chart illustrating a moving object contourtracking method according to another embodiment of the presentinvention;

FIG. 14 is a schematic flow chart illustrating a myocardial motionanalysis method according to an embodiment of the present invention;

FIG. 15 shows an example of a point linking pair according to theembodiment of the present invention;

FIG. 16 is a schematic diagram illustrating a myocardial motioncomponent according to an embodiment of the present invention;

FIG. 17 is a schematic diagram illustrating the smoothing of a motioncomponent time series according to an embodiment of the presentinvention;

FIG. 18 shows a view of myocardial strains according to an embodiment ofthe present invention;

FIG. 19 is a schematic flow chart illustrating a myocardial motionanalysis method according to another embodiment of the presentinvention;

FIG. 20 is a schematic block diagram illustrating a moving objectcontour tracking apparatus according to an embodiment of the presentinvention;

FIG. 21 is a schematic block diagram illustrating a contour trackingsection according to an embodiment of the present invention;

FIG. 22 is a schematic block diagram illustrating a moving objectcontour tracking apparatus according to another embodiment of thepresent invention;

FIG. 23 is a schematic block diagram illustrating an initial contouracquisition section according to an embodiment of the present invention;

FIG. 24 is a schematic block diagram illustrating an endocardial contouracquisition section according to an embodiment of the present invention;

FIG. 25 is a schematic block diagram illustrating an initial contouracquisition section according to another embodiment of the presentinvention;

FIG. 26 shows a schematic block diagram illustrating an epicardialcontour acquisition section according to an embodiment of the presentinvention;

FIG. 27 is a schematic block diagram illustrating a moving objectcontour tracking apparatus according to another embodiment of thepresent invention;

FIG. 28 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to an embodiment of the present invention;

FIG. 29 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to another embodiment of the presentinvention;

FIG. 30 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to still another embodiment of the presentinvention;

FIG. 31 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to yet another embodiment of the presentinvention;

FIG. 32 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to a further embodiment of the presentinvention;

FIG. 33 shows a computer structure capable of implementing themethods/apparatuses disclosed in the embodiments of the presentinvention.

DETAILED DESCRIPTION

According to an embodiment, A moving object contour tracking apparatusfor tracking a contour of a periodically deforming object in an imageslice time series, the image slice time series comprising a plurality ofimage slices acquired at a plurality of time points in a motion periodof the moving object, the moving object contour tracking apparatusincludes a contour tracking section, a contour comparison section and acontour correction section. The contour tracking section configured toperform, by taking an initial contour of the moving object in apredetermined image slice of the image slice time series as a startingcontour, contour tracking in the image slice time series in a first timedirection to acquire a first contour of the moving object in each imageslice of the image slice time series, and perform, by taking the initialcontour as a starting contour, contour tracking in the image slice timeseries in a second time direction to acquire a second contour of themoving object in each image slice of the image slice time series. Thecontour comparison section configured to calculate a similarity betweenthe first contour of the moving object in the predetermined image sliceand the initial contour as a first similarity and a similarity betweenthe second contour of the moving object in the predetermined image sliceand the initial contour as a second similarity. The contour correctionsection configured to take the contours in the image slices tracked bythe contour tracking section in a contour tracking directioncorresponding to a greater one of the first and second similarities asthe contours of the moving object in the respective image slices.

The following presents a simplified summary of the present invention toprovide a basic understanding of some aspects of the present invention.It should be understood that the summary is not an exhaustive summary ofthe present invention. It is not intended to identify the key orcritical parts of the present invention, nor intended to limit the scopeof the present invention. It only aims to present some concepts in asimplified form as a prelude to the more detailed description that is tobe discussed later.

It is an object of the present invention to provide a moving objectcontour tracking method and apparatus for extracting a contour of amoving object accurately from an image slice time series. It is anotherobject of the present invention to provide a moving object contourtracking method and apparatus for extracting a moving object contouraccurately from a three-dimensional image time series. It is a furtherobject of the present invention to provide a myocardial motion analysismethod and apparatus for analyzing the motion of a myocardium of a leftventricle stably from a medical image slice time series. It is a stillfurther object of the present invention to provide a myocardial motionanalysis method and apparatus for analyzing the motion of a myocardiumof a left ventricle stably from a three-dimensional medical image timeseries.

In accordance with an aspect of the present invention, there is provideda moving object contour tracking method for tracking a contour of aperiodically deforming object in an image slice time series, the imageslice time series comprising a plurality of image slices acquired at aplurality of time points in a motion period of the moving object. Themethod includes: performing, by taking an initial contour of the movingobject in a predetermined image slice of the image slice time series asa starting contour, contour tracking in the image slice time series in afirst time direction to acquire a first contour of the moving object ineach image slice of the image slice time series, wherein a last imageslice is taken as the previous image slice of a first image slice in thefirst time direction; performing, by taking the initial contour as astarting contour, contour tracking in the image slice time series in asecond time direction to acquire a second contour of the moving objectin each image slice of the image slice time series, wherein a last imageslice is taken as the previous image slice of a first image slice in thesecond time direction; calculating a similarity between the firstcontour of the moving object in the predetermined image slice and theinitial contour as a first similarity and a similarity between thesecond contour of the moving object in the predetermined image slice andthe initial contour as a second similarity; and taking the contours inthe image slices tracked by the contour tracking section in a contourtracking direction corresponding to a greater one of the first andsecond similarities as the contours of the moving object in therespective image slices.

In accordance with another aspect of the present invention, there isprovided a moving object contour tracking method for tracking thecontour of a periodically deforming moving object in a three-dimensionalimage time series, the three-dimensional image time series comprising aplurality of three-dimensional images acquired at a plurality of timepoints in a motion period of the moving object, each of thethree-dimensional images consisting of a plurality of paralleltwo-dimensional image slices, and the two-dimensional image sliceslocated at the same location in the plurality of three-dimensionalimages forming an image slice time series. The method includes: trackinga contour of the moving object in each image slice time series using themoving object contour tracking method according to the above aspect ofthe present invention. The contours of the moving object in theplurality of two-dimensional image slices at the same time point form athree-dimensional contour of the moving object at this time point.

In accordance with another aspect of the present invention, there isprovided a myocardial motion analysis method for analyzing a motion of amyocardium of a left ventricle in a medical image slice time series, themedical image slice time series comprising a plurality of image slicesacquired with respect to a section of the left ventricle intersectedwith a long axis of the left ventricle at a plurality of time points ina cardiac cycle. The method includes: acquiring an endocardial contourand an epicardial contour of the left ventricle in each image slice;configuring contour points on the endocardial contour and the epicardialcontour in a reference image slice of the image slice time series as aplurality of point linking pairs, each point linking pair comprising acontour point on the endocardial contour and a contour point on theepicardial contour, and the two contour pints of each point linking pairbeing located on the same normal of a reference contour of a leftventricle wall in the reference image slice; determining locations ofeach point linking pair in other image slices of the image slice timeseries; and calculating, according to the locations of the plurality ofpoint linking pairs in adjacent image slices of the image slice timeseries, a motion vector of the myocardium of the left ventricle betweenthe adjacent image slices, the myocardium being defined by theendocardial contour and the epicardial contour.

In accordance with another aspect of the present invention, there isprovided a myocardial motion analysis method for analyzing a motion of amyocardium of a left ventricle in a three-dimensional medical image timeseries, the three-dimensional medical image time series comprising aplurality of three-dimensional images acquired at a plurality of timepoints in a cardiac cycle, each of the three-dimensional imagesconsisting of a plurality of parallel two-dimensional image slices thatare intersected with a long axis of the left ventricle, and thetwo-dimensional image slices located at the same location in thethree-dimensional images forming an image slice time series. The methodincludes: analyzing the motion of the myocardium of the left ventriclein each medical image slice time series using the myocardial motionanalysis method according to the above aspect of the present invention.The motions of the myocardium in the plurality of two-dimensional imageslices at the same time point form a motion of the left ventricle atthis time point.

In accordance with another aspect of the present invention, there isprovided a moving object contour tracking apparatus for tracking acontour of a periodically deforming object in an image slice timeseries, the image slice time series comprising a plurality of imageslices acquired at a plurality of time points in a motion period of themoving object. The apparatus includes: a contour tracking sectionconfigured to perform, by taking an initial contour of the moving objectin a predetermined image slice of the image slice time series as astarting contour, contour tracking in the image slice time series in afirst time direction to acquire a first contour of the moving object ineach image slice of the image slice time series, wherein a last imageslice is taken as the previous image slice of a first image slice in thefirst time direction, and perform, by taking the initial contour as astarting contour, contour tracking in the image slice time series in asecond time direction to acquire a second contour of the moving objectin each image slice of the image slice time series, wherein a last imageslice is taken as the previous image slice of a first image slice in thesecond time direction; a contour comparison section configured tocalculate a similarity between the first contour of the moving object inthe predetermined image slice and the initial contour as a firstsimilarity and a similarity between the second contour of the movingobject in the predetermined image slice and the initial contour as asecond similarity; and a contour correction section configured to takethe contours in the image slices tracked by the contour tracking sectionin a contour tracking direction corresponding to a greater one of thefirst and second similarities as the contours of the moving object inthe respective image slices.

In accordance with another aspect of the present invention, there isprovided a moving object contour tracking apparatus for tracking acontour of a periodically deforming moving object in a three-dimensionalimage time series, the three-dimensional image time series comprising aplurality of three-dimensional images acquired at a plurality of timepoints in a motion period of the moving object, each of thethree-dimensional images consisting of a plurality of paralleltwo-dimensional image slices, and the two-dimensional image sliceslocated at the same location in the plurality of three-dimensionalimages forming an image slice time series. The apparatus includes: atracking section implemented by the moving object contour trackingapparatus according to the above aspect of the present invention andconfigured to track a contour of the moving object in each image slicetime series. The contours of the moving object in the plurality oftwo-dimensional image slices at the same time point form athree-dimensional contour of the moving object at this time point.

In accordance with another aspect of the present invention, there isprovided a myocardial motion analysis apparatus for analyzing a motionof a myocardium of a left ventricle in a medical image slice timeseries, the medical image slice time series comprising a plurality ofimage slices acquired with respect to a section of the left ventricleintersected with a long axis of the left ventricle at a plurality oftime points in a cardiac cycle. The apparatus includes: a contouracquisition section configured to acquire an endocardial contour and anepicardial contour of the left ventricle in each image slice; a pointlinking pair configuration section configured to configure contourpoints on the endocardial contour and the epicardial contour in areference image slice of the image slice time series as a plurality ofpoint linking pairs, each point linking pair comprising a contour pointon the endocardial contour and a contour point on the epicardialcontour, and the two contour points of each point linking pair beinglocated on the same normal of a reference contour of a left ventriclewall in the reference image slice; a point linking pair tracking sectionconfigured to determine locations of each point linking pair in otherimage slices of the image slice time series; and a motion vectorcalculation section configured to calculate, according to the locationsof the plurality of point linking pairs in adjacent image slices of theimage slice time series, a motion vector of the myocardium of the leftventricle between the adjacent image slices, the myocardium beingdefined by the endocardial contour and the epicardial contour.

In accordance with another aspect of the present invention, there isprovided a myocardial motion analysis apparatus for analyzing a motionof a myocardium of a left ventricle in a three-dimensional medical imagetime series, the three-dimensional medical image time series comprisinga plurality of three-dimensional images acquired at a plurality of timepoints in a cardiac cycle, each of the three-dimensional imagesconsisting of a plurality of parallel two-dimensional image slices thatare intersected with a long axis of the left ventricle, and thetwo-dimensional image slices located at the same location in thethree-dimensional images forming an image slice time series. Theapparatus comprising: an analysis section implemented by the myocardialmotion analysis apparatus according to the above aspect of the presentinvention, and configured to analyze the motion of the myocardium of theleft ventricle in each medical image slice time series. The motions ofthe myocardium generated in the plurality of two-dimensional imageslices at the same time point form a motion of the left ventricle atthis time point.

Moreover, according to still another aspect of the present invention,there is provided a computer program for realizing the foregoingmethods.

Additionally, according to still a further aspect of the presentinvention, there is provided a computer program product, which is in theform of at least a computer readable medium, on which computer programcodes for realizing the foregoing methods are recorded.

Embodiments of the present invention are described below with referenceto the accompanying drawings. The sections and features described in afigure or an embodiment of the present invention can be combined withthe sections and features shown in one or more other figures orembodiments. It should be noted that, for the purpose of clarity,representations and descriptions of sections and processes which areknown to those skilled in the art or are not related to the presentinvention, are not presented in the drawings and the description.

Exemplary embodiments of the present invention are described below inthe following order:

1. Moving object contour tracking method

2. Moving object contour tracking method for a three-dimensional imagetime series

3. Myocardial motion analysis method

4. Myocardial motion analysis method for a three-dimensional medicalimage time series

5. Moving object contour tracking apparatus

6. Moving object contour tracking apparatus for a three-dimensionalimage time series

7. Myocardial motion analysis apparatus

8. Myocardial motion analysis apparatus for a three-dimensional medicalimage time series

9. Computer structure capable of implementing the methods/apparatusesdisclosed in the embodiments of the present invention

<1. Moving Object Contour Tracking Method>

The moving object contour tracking method according to embodiments ofthe present invention is described below with reference to FIG. 1-FIG.12B.

The moving object contour tracking method according to the embodimentsof the present invention is configured to track a contour of a movingobject which deforms periodically in an image slice time series. Animage slice time series includes a plurality of image slices that arerespectively acquired for the moving object at a plurality of timepoints in a motion period of the moving object. It should be appreciatedthat the moving object contour tracking method provided in theembodiments of the present invention can be used for tracking a contourof a moving object in various types of image slice time series. As anexample but not a limitation, the image slice time series can be amedical image series formed by examinee data obtained through a medialdiagnostic device. The medial diagnostic device includes but is notlimited to an X-ray imaging diagnostic device, an ultrasonic diagnosticimaging device, a computed tomography (CT) device, a magnetic resonanceimaging (MRI) diagnostic device and a positron emission tomography (PET)device and the like.

FIG. 1 is a schematic flow chart illustrating a moving object contourtracking method according to an embodiment of the present invention. Inthis embodiment, a contour of a moving object is tracked respectively intwo time directions, and the tracking result with a higher reliabilityis taken as the contour of the moving object, thus improving theaccuracy of the contour tracking.

As shown in FIG. 1, in step S110, contour tracking is performed in animage slice time series in a first time direction to acquire a firstcontour of the moving object in each image slice. In performing thecontour tracking, an initial contour of the moving object in apredetermined image slice of the image slice time series is taken as astarting contour, and the last image slice is taken as the previousimage slice of a first image slice in the first time direction. Here,the first time direction may be a time elapsing direction from former tolater, or a direction from later to former which is opposite to the timeelapsing direction.

As the moving object is deforming periodically and the image slice timeseries includes the image slices acquired in a motion period of themoving object, the first image slice has a motion correlation with thelast image slice, that is, the contours of the moving object in thefirst and the last image slices are similar. Thus, the last image slicein the first time direction can be taken as the previous image slice ofthe first image slice without influencing the accuracy of the contourtracking.

It should be appreciated that the predetermined image slice of the imageslice time series here may be an image slice a relatively accurateinitial contour of which can be acquired easily. The predetermined imageslice may be designated manually or be recognized from the image slicetime series using an existing technical method based on a predeterminedimage slice characteristic.

In step S120, the contour tracking is performing in the image slice timeseries in a second time direction to acquire a second contour of themoving object in each image slice. Similarly, in performing the contourtracking, the initial contour of the moving object in the predeterminedimage slice is taken as a starting contour. Additionally, the last imageslice is taken as the previous image slice of a first image slice in thesecond time direction. Here, the second time direction, which is adirection opposite to the first time direction, may be a direction fromlater to former which is opposite to the time elapsing direction, or thetime elapsing direction from former to later.

Similarly, as the moving object is deforming periodically and the imageslice time series includes the image slices acquired in a motion periodof the moving object, taking the last image slice in the second timedirection as the previous image slice of the first image slice will notinfluence the accuracy of the contour tracking.

In step S130, a similarity between the first contour of the movingobject in the predetermined image slice and the initial contour of themoving object in the predetermined image slice is calculated as a firstsimilarity, and a similarity between the second contour of the movingobject in the predetermined image slice and the initial contour of themoving object in the predetermined image slice is calculated as a secondsimilarity. In both of the first and second time directions, the contourof the moving object in the predetermined image slice acquired throughthe contour tracking is the contour acquired by the last tracking in thecontour tracking. In addition, as stated above, taking the last imageslice in the first or second time direction as the previous image sliceof the first image slice will not influence the accuracy of the contourtracking. Therefore, if the similarity between a tracked contour and theinitial contour of the moving object in the predetermined image slice ishigher, then it may be determined that the contour tracking performed inthe respective time direction has a higher accuracy, that is, a higherreliability.

In step S140, the contours in the image slices tracked in the contourtracking direction (the first or second time direction) corresponding toa greater one of the first and second similarities are taken as thecontours of the moving object in the respective image slices.

By performing complete contour tracking respectively in the two timedirections and comparing the tracked contours with the initial contour,a tracked contour with a higher reliability can be selected as thecontour of the moving object, thereby improving the accuracy of thecontour tracking.

In order to facilitate understanding, FIG. 2 shows an applicationexample of the moving object contour tracking method according to theembodiment of the present invention. This example shows an image slicetime series consisting of a plurality of image slices that are acquiredby an MRI device from a section of a left ventricle intersected with along axis of the left ventricle (that is, the long axis of a heart) at aplurality of time points of a cardiac cycle. The image slice time seriesincludes 11 image slices that are numbered from 1 to 11 in time sequencefrom former to later. In each image slice, an epicardial contour of theleft ventricle is denoted with a solid line, and an endocardial contourof the left ventricle is denoted with a dotted line. Only an epicardialcontour tracking process is described herein, and an endocardial contourtracking process is a similar process and therefore is not describedrepeatedly.

In this example, the image slice 6, which is an image slice in anend-systolic phase, is taken as a predetermined image slice. At theend-systolic phase, the left ventricle presents an obvious edge and aregular shape, which facilitates the contour determination of the leftventricle. The image slice in the end-systolic phase can be designatedmanually or recognized among the image slice time series using anyproper existing method. As an example but not a limitation, the image inthe end-systolic phase can be detected from the image slice time seriesaccording to area, or determined according to an external signal bycomparison with a synchronous electrocardiogram.

By taking an initial epicardial contour of the left ventricle in theimage slice 6 as a starting contour to perform contour tracking in thefirst time direction (as an example, the first time direction in thisexample is the time elapsing direction) indicated by an arrow shown inFIG. 2, first epicardial contours C71 to C111 and C11 to C61 of the leftventricle in the image slices 7-11 and 1-6 are acquired one by one. Inthis tracking process, the last image slice 11 in the first timedirection is taken as the previous image slice of the first image slice1.

By taking the initial epicardial contour of the left ventricle in theimage slice 6 as a starting contour to perform contour tracking in thesecond time direction (as an example, the second time direction in thisexample is a direction opposite to the time elapsing direction) shown byan arrow, second epicardial contours C52 to C12 and C112 to C62 of theleft ventricle in the image slices 5-1 and 11-6 are acquired one by one.In this tracking process, the last image slice 1 in the second timedirection is taken as the previous image slice of the first image slice11.

It can be seen that in the tracking process in the first time direction,a tracking error occurs in the epicardial contour in the image slice 9and is then sequentially propagated to the epicardial contour C61 in theimage slice 6. It can be known by calculation that the similaritybetween the second contour C62 in the image slice 6 serving as thepredetermined image slice and the initial contour C60 is higher than thesimilarity between the first contour C61 and the initial contour C60.Consequently, it can be determined that the contour tracking in thesecond time direction is more accurate than that in the first timedirection. Thus, the epicardial contours acquired in the second timedirection can be taken as the epicardial contours of the left ventriclein the respective image slices.

It should be noted that a heart image, which is provided herein as anexample for describing the moving object contour tracking method andapparatus, is not to be construed as a limitation to the presentinvention. To the contrary, the present invention can be applied to anyimage containing a moving object that deforms periodically.

In order to decrease the amount of calculation, according to anotherembodiment of the present invention, a first turn of contour tracking isperformed at first, and a second turn of contour tracking is performedto correct the result of the first turn of contour tracking only when itis determined according to the result of the first turn of contourtracking that the first turn of contour tracking may have an error. As aspecific implementation mode, in an image slice time series including nimage slices, by taking an initial contour of the moving object in thesth image slice as a starting contour, a turn of contour tracking isperformed respectively in a direction from the (s−1)th to first imageslices and a direction from the (s+1)th to the nth image slices toacquire the first contours of the moving object in the (s−1)th to firstimage slices and in the (s+1)th to nth image slices, wherein srepresents the number of the predetermined image slice and 1≦s≦n. Thesimilarity between the first contour of the moving object in the firstimage slice and the first contour of the moving object in the nth imageslice is calculated. If the similarity between the first contour of themoving object in the first image slice and that of the moving object inthe nth image slice is lower than a predetermined threshold, indicatingthat there may be an error in the first turn of contour tracking, asecond turn of contour tracking is performed. In the second turn ofcontour tracking, by taking the first contour of the moving object inthe first image slice as a starting contour, the contour tracking isperformed in a direction from the nth image slice to the sth image sliceto acquire the second contours of the moving object in the nth to(s−1)th image slices and a first contour of the moving object in the sthimage slice; and by taking the first contour of the moving object in thenth image slice as a starting contour, the contour tracking is performedin a direction from the first image slice to the sth image slice toacquire the second contours of the moving object in the first to sthimage slices. The similarity between the first contour and the initialcontour of the moving object in the sth image slice and the similaritybetween the second contour and the initial contour of the moving objectin the sth image slice are respectively calculated. If the similaritybetween the first contour and the initial contour of the moving objectin the sth image slice is greater than that between the second contourand the initial contour of the moving object in the sth image slice, thefirst contours of the moving object in the (s−1)th to first image slicesare taken as the contours of the moving object in the (s−1)th to firstimage slices, and the contours of the moving object in the nth to(s+1)th image slices are taken as the contours of the moving object inthe nth to (s+1)th image slices, vice versa.

For instance, for the image slice time series shown in FIG. 2, theinitial contour in the image slice 6 can be taken as a starting contourto track the epicardial contours in the image slices 5-1 in a directionopposite to the time elapsing direction and the epicardial contours inthe image slices 7-11 in the time elapsing direction. Here, consumingthat the image slice time series shown in FIG. 2 includes a plurality ofimage slices acquired in one motion period of the left ventricle, imageslices 1 and 11 are two adjacent image slices in location in the motionperiod. The epicardial contours in the image slices 1 and 11 arecompared. If the difference between the epicardial contours in imageslices 1 and 11 is small, then it is considered that the trackingresults acquired in the two directions both are accurate and no secondturn of tracking is needed. If the difference between the epicardialcontours in image slices 1 and 11 is big, it is considered that there isan error in the tracking in one of the two directions, and then, thecontour tracking of epicardial contour is continued in the image slices1-6 (starting from the image slice 11) in time elapsing direction, andcontinued in the image slices 11-6 (starting from the image slice 1) inthe direction opposite to the time elapsing direction. Then thesimilarity comparison as described above is carried out to select theresult acquired in the tracking direction with a higher similarity asthe epicardial contours of the left ventricle.

In addition, according to another embodiment of the present invention,after the similarity comparison is carried out, the contours acquired inthe contour tracking direction corresponding to the lower similarity maybe corrected with the contours acquired in the contour trackingdirection corresponding to the greater similarity so as to acquire finalcontours. Any proper existing method can be used to perform thecorrection. As an example but not a limitation, the average of thecontours acquired in the two contour tracking directions may becalculated as the final contours.

Additionally, when the image slice time series fails to cover a completemotion period, the first image slice and the last image slice are not soadjacent in the motion period as they are in the case where the imageslice time series covers a complete motion period, and consequentially,the similarity between the first image slice and the last image slicemay be lower than that in the case where the image slice time seriescovers a complete motion period. In this situation, the image slicescorresponding to the uncovered part of the motion period may bepredicted through image interpolation, and then the predicted imageslices and the original image slices are used together to perform thecontour tracking, so as to eliminate the influence caused by the lowersimilarity between the first and last image slices and to improve theaccuracy of the contour tracking.

Whether the image slice time series covering a complete motion periodcan be determined using existing methods. For example, it can bedetermined by comparing the time information carried by each image slicewith the motion period information of the moving object that may beexternally input. If the time interval spanned by the image slice timeseries (that is, the time interval between the first and last imageslices in the image slice time series) is shorter than the motionperiod, it is determined that the image slice time series fails to coverthe complete motion period.

The one or more image slices corresponding to the uncovered part of themotion period may be predicted using any proper existing imageinterpolation method, for example, the nearest-neighbor interpolationand the bilinear interpolation. For instance, in the case where thecontour tracking is performed in the first time direction, the lastimage slice in the first time direction is taken as a source image andthe first image slice in the first time direction is taken as a targetimage slice to predict the one or more image slices between the last andfirst image slices using an image interpolation method; and in the casewhere the contour tracking is performed in the second time direction,the last image slice in the second time direction is taken as the sourceimage and the first image slice in the second time direction is taken asthe target image slice to predict the one or more image slices betweenthe last and first image slices using an image interpolation method.

The number of the image slices to be predicted can be determinedaccording to the ratio of the length of the uncovered part of the motionperiod to the interval between adjacent image slices of the image slicetime series.

Then, tracking is performed in the image slice time series consisting ofthe original image slices and the predicted image slices is tracked ineach time direction.

For instance, for the example shown in FIG. 2, the interval between theimage slices 1 and 11 can be compared. If the interval is smaller thanthe cardiac cycle of the left ventricle, then the image slices to beinterpolated between the image slices 1 and 11 are respectivelypredicted in the first and second time directions using an imageinterpolation method. Then, an image slice time series including theoriginal image slices 1-11 and the interpolated image slices is trackedin the contour tracking in the two time direction.

In the moving object contour tracking method according to the embodimentof the present invention, the contour tracking step may be realizedusing any proper existing method without limitation. As an example, FIG.3 is a schematic flow chart illustrating a contour tracking stepaccording to an embodiment of the present invention.

As shown in FIG. 3, starting from a predetermined image slice, if it isdetermined in step S310 that there exists a next image slice of theimage slice time series, the process proceeds to perform the contourtracking from step S320 to step S360; and otherwise, the process isended.

In step S320, the contour of the moving object in the current imageslice is expanded to obtain a contour region of interest (ROI). Forinstance, the contour of the moving object can be expanded with apredetermined width to obtain the contour ROI.

In step S330, the contour ROI is divided into a plurality of trackingcells with a predetermined size.

In order to facilitate understanding, FIG. 4 shows an example of acontour ROI and tracking cells.

In step S340, locations of the plurality of tracking cells in the nextimage slice is obtained by template matching. Here, the templatematching for the tracking cells can be carried out using any properexisting template matching method, which will not be described in detailherein.

In step S350, the motion vectors of the plurality of tracking cells fromthe current image slice to the next image slice are calculated accordingto the locations of the plurality of tracking cells in the next imageslice. For instance, the average location of the pixels in a trackingcell or the location of the central pixel of the tracking cell can betaken as the location of the tracking cell.

In step S360, the contour of the moving object in the next image sliceis acquired based on the contour of the moving object in the currentimage slice and the motion vectors of the plurality of tracking cellsfrom the current image slice to the next image slice.

As a specific implementation mode, a weighted average of the motionvectors of tracking cells within a predetermined range and adjacent toeach contour point on the contour of the moving object in the currentimage slice can be calculated as a motion vector of the contour pointfrom the current image slice to the next image slice. Then, the contourof the moving object in the current image slice is moved according tothe motion vector of each contour point on the contour of the movingobject in the current image slice to acquire the contour of the movingobject in the next image slice.

In the exemplary embodiments described above, the examples are explainedin which contour tracking is performed in a plurality of image slicesacquired at a plurality of time points in a motion period of the movingobject. However, the embodiments are not limited to these examples. Forexample, contour tracking is performed in a plurality of image slicesacquired at a plurality of time points in a predetermined period of themoving object. For example, among the image slices 1-11 shown in FIG. 2,first epicardial contours C41 to C61 of the left ventricle in the imageslices 4-6 are acquired one by one. second epicardial contours C82 toC62 of the left ventricle in the image slices 8-6 are acquired one byone. Then the similarity comparison as described above is carried out toselect the result acquired in the tracking direction with a highersimilarity as the epicardial contours of the left ventricle.

In the moving object contour tracking method according to an embodimentof the present invention, the initial contour of the moving object inthe predetermined image slice is acquired in advance. The initialcontour of the moving object can be acquired using any existing method,or can be depicted manually. As an example, a method for acquiring theinitial contour of the moving object according to an embodiment of thepresent invention is described below.

In the following embodiment, the moving object is a left ventricle, theimage slice time series includes a plurality of image slices that areacquired with respect to a section of the left ventricle intersectedwith the long axis of the left ventricle at a plurality of time pointsin a cardiac cycle. The left ventricle has an endocardial contour and anepicardial contour, and a method for acquiring an initial endocardialcontour and a method for acquiring an initial epicardial contour arerespectively described below.

In the following embodiment, considering that the contours of theendocardium and the epicardium of the left ventricle are both curves,the contour of the endocardium tends to be influenced by a papillarymuscle, and the contour of the epicardium is relatively blurry, theoriginal image slices are converted to a polar coordinate system so thatthe contours of the endocardium and the epicardium can be extracted fromthe image slices more accurately.

In order to facilitate understanding, FIG. 5 shows a schematic diagramillustrating a conversion relationship between a Euclidean coordinatesystem and a polar coordinate system. In this figure, the origin of theEuclidean coordinate system corresponds to the pole of the polarcoordinate system. The horizontal coordinate in the polar coordinatesystem represents the angle of a line between a point in the Euclideancoordinate system and the origin with respect to the positive directionof the horizontal direction of the Euclidean coordinate system, and thevertical coordinate in the polar coordinate system represents a distancebetween the origin and a point in the Euclidean coordinate system. Afterbeing converted to the polar coordinate system, the circles withdifferent radiuses in the Euclidean coordinate system are presented asstraight lines with different heights. On the other hand, after beingconverted into the Euclidean coordinate system, the straight lines withdifferent heights in the polar coordinate system are presented ascircles with different radiuses.

FIG. 6 is a schematic flow chart illustrating a method for acquiring aninitial contour of a left ventricle according to an embodiment of thepresent invention. In this embodiment, an endocardial contour of theleft ventricle is acquired as the initial contour of the left ventricle.

As shown in FIG. 6, in step S610, a predetermined image slice isconverted to the polar coordinate system. Here, as an example, thepredetermined image slice may be an image slice in an end-systolicphase. In actual applications, in order to decrease the amount ofcalculation, only the motion area part in the predetermined image slice,rather than the whole image slice, may be converted to the polarcoordinate system.

In step S620, the endocardial contour of the left ventricle is acquiredin the polar coordinate system as the initial contour of the leftventricle in the predetermined image slice. In the polar coordinatesystem, the contour of the endocardium is approximate to a straightline. In addition, in the polar coordinate system, various kinds ofinformation projected in the horizontal direction (the direction of thehorizontal axis) such as brightness (typically represented with a pixelvalue) and edge can be used, which will be described later.

In step S630, the initial contour of the left ventricle acquired in thepolar coordinate system is mapped to the original predetermined imageslice. In the left ventricle, the endocardial contour line obtained by acommon method may be relatively small due to the influence of thepapillary muscle. Therefore, in the acquisition of the endocardialcontour of the left ventricle, it is an important task to eliminate theinfluence of the papillary muscle and to contain the papillary muscle ina range defined by the contour line of the endocardium so as to obtain abigger and more accurate endocardial contour.

The endocardial contour of the left ventricle in the predetermined imageslice can be acquired in the polar coordinate system using any properexisting method. As an example, FIG. 7 shows a schematic flow chartillustrating acquisition of an endocardial contour of a left ventricleaccording to an embodiment of the present invention. In this embodiment,a rough location of the endocardial contour is determined in the polarcoordinate system using a horizontal projection of an image slice, andthen the endocardial contour is acquired from the edge image of theimage slice using a straight line detection method.

As shown in FIG. 7, in step S710, edges are detected in thepredetermined image slice to acquire an edge image of the predeterminedimage slice.

In step S720, a radius of the endocardial contour of the left ventriclein the predetermined image slice is acquired in the polar coordinatesystem using the horizontal projection of a gray scale image of thepredetermined image slice. It can be seen from the original image sliceof the left ventricle shown in FIG. 2 that the gray scale of themyocardium of the left ventricle is smaller than the part inside theleft ventricle. Accordingly, the location where a pixel value dropssharply in the horizontal projection of the gray scale image of theimage slice can be taken as the location of the radius of theendocardial contour.

Then, in step S730, the endocardial contour of the left ventricle isacquired in the polar coordinate system from the edges nearby the radiusof the endocardial contour of the left ventricle using a straight linedetection method.

In order to facilitate understanding, FIG. 8A shows an example of a grayscale image of a predetermined image slice in a polar coordinate system,and FIG. 8B shows an example of a horizontal projection the gray scaleimage shown in FIG. 8A. In FIG. 8B, the horizontal coordinate representsa row in the gray scale image of the image slice, and the verticalcoordinate represents the sum or average of the pixel values in a row.An image slice is divided into rows by taking one or more pixels as aunit, depending on different demands on accuracy. As shown in FIG. 8B,the location where the sum or average of pixel values drops sharply isdetermined as the location of the radius Rendo of the endocardialcontour.

In the foregoing embodiment, the straight line detection method may be aHough transformation method. In Comparison with other straight linedetection methods, which take into consideration an edge pixel with asmall radius and therefore tends to be influenced by the papillarymuscle, the Hough transformation method, when used for fitting edgepixels (also referred to as edge points), can acquire a contourcontaining the majority of edge points and eliminate the influencecaused by edge points such as the papillary muscle and noise.

FIG. 9 is a schematic flow chart illustrating acquisition of an initialcontour of a left ventricle according to another embodiment of thepresent invention. In this embodiment, the epicardial contour of theleft ventricle is acquired as the initial contour of the left ventricle.

As shown in FIG. 9, in step S910, a predetermined image slice isconverted to a polar coordinate system. Similarly, as an example, thepredetermined image slice may be an image slice in an end-systolicphase. In actual applications, in order to decrease the amount ofcalculation, only a motion area part in the predetermined image slicerather than the whole image slice may be converted to the polarcoordinate system. In step S920, the epicardial contour of the leftventricle is acquired in the polar coordinate system as the initialcontour of the left ventricle in the predetermined image slice. In stepS930, the initial contour of the left ventricle acquired in the polarcoordinate system is mapped to the original predetermined image slice.

The epicardial contour of the left ventricle in the predetermined imageslice can be acquired in the polar coordinate system using any properexisting method. As an example, FIG. 10 is a schematic flow chartillustrating acquisition of an epicardial contour of a left ventricleaccording to an embodiment of the present invention. In this embodiment,edge pixels of an endocardial contour and a thickness of a myocardiumare determined using the horizontal projection of an image slice todetermine a rough location of the epicardial contour in the polarcoordinate system, and then the epicardial contour can be acquired froman edge image of the image slice using a curve fitting method.

As shown in FIG. 10, in step S1010, edges in the predetermined imageslice are detected to acquire an edge image of the predetermined imageslice.

In step S1020, a radius of the endocardial contour of the left ventriclein the predetermined image slice is acquired in the polar coordinatesystem using the horizontal projection of a gray scale image of thepredetermined image slice.

In step S1030, the thickness of the myocardium of the left ventricle isdetermined in the polar coordinate system using a horizontal projectionof an edge image of the predetermined image slice and the radius of theendocardial contour, thereby acquiring a radius of the epicardium of theleft ventricle in the predetermine image slice.

In step S1040, the epicardial contour of the left ventricle is acquiredfrom the edges nearby the radius of the epicardial contour of the leftventricle in the polar coordinate system using any curve fitting methodsuch as a least square method.

In order to facilitate understanding, FIG. 11A shows an example of anedge image of a predetermined image slice in a polar coordinate system,and FIG. 11B shows an example of a horizontal projection of the edgeimage shown in FIG. 11A. In FIG. 11B, the horizontal coordinaterepresents a row in the edge image of the image slice, and the verticalcoordinate represents the sum or average of the pixel values in a row.The predetermined image slice is divided into rows by taking one or morepixels as a unit, depending on different demands on accuracy. As shownin FIG. 11B, a location where the sum or average of pixel values dropssharply is determined as the location of the radius Rendo of theendocardial contour. In the edge image, as the myocardium part betweenthe endocardial contour and the epicardial contour substantiallycontains no edge, there is a gap between the endocardial contour and theepicardial contour in the horizontal projection. Thus, as shown in FIG.11B, the gap immediately next to the location of the radius Rendo of theendocardial contour is determined as a thickness of the myocardiumbetween the endocardial contour and the epicardial contour, and thelocation behind the gap is the location of the radius Repi of theepicardial contour.

In order to facilitate understanding, FIG. 12A shows examples of anendocardial contour and an epicardial contour acquired in a polarcoordinate system according to the foregoing embodiment. In FIG. 12A,the upper contour line represents an endocardial contour, and the lowercontour line represents an epicardial contour. FIG. 12B shows an exampleof conversion of the endocardial contour and the epicardial contouracquired in FIG. 12A to an original image slice. The endocardial contourshown in FIG. 12B is relatively smooth and includes no protrusion, thatis, the influence of the papillary muscle is eliminated.

<2. Moving Object Contour Tracking Method for a Three-Dimensional ImageTime Series>

FIG. 13 is a schematic flow chart illustrating a moving object contourtracking method according to another embodiment of the presentinvention.

The moving object contour tracking method provided according to thisembodiment is used to track the contour of a periodically deformingobject in a three-dimensional image time series. The three-dimensionalimage time series includes a plurality of three-dimensional images thatare acquired at a plurality of time points in a motion period of themoving object. Each of the three-dimensional images consists of aplurality of parallel two-dimensional image slices. The two-dimensionalimage slices located at the same location in the three-dimensionalimages form an image slice time series.

As shown in FIG. 13, in this method, in step S1310, the contour of themoving object is respectively tracked in each image slice time series.Here, the contour of the moving object is tracked in each image slicetime series using the moving object contour tracking method described inthe part <1. Moving object contour tracking method>. The contours of themoving object in the plurality of two-dimensional image slices at thesame time point form a three-dimensional contour of the moving object atthis time point.

In a three-dimensional image time series, there may be some image slicetime series which are beyond the real range of the moving object. Thecontours of the moving object tracked in these image slice time seriesare unreal and, if being adopted, will undermine the accuracy of thesubsequent calculation of some parameters of the moving object. On thisground, in an embodiment of the present invention, before the contourtracking of the moving object, such undesired image slice time series asdescribed above are determined, and are not subjected to the contourtracking or are directly deleted to avoid the influence on the accuracyof the subsequent parameter calculation.

For a three-dimensional image time series acquired by an MRI device in ashort axis direction of a heart, when the left ventricle is taken as amoving object, the two image slice time series corresponding to the twoends of the moving object are respectively the image slice time seriesat a base part and that at an apex part.

The image slice time series corresponding to the two ends of the movingobject may be recognized using any proper existing method that will notbe described herein in detail.

<3. Myocardial Motion Analysis Method>

A myocardial motion analysis method according to embodiments of thepresent invention is described below with reference to FIG. 14-FIG. 18.The myocardial motion analysis method according to the embodiments ofthe present invention is used for analyzing the motion of a myocardiumof a left ventricle in a medical image slice time series. A medicalimage slice time series includes a plurality of image slices that areacquired with respect to a section of the left ventricle intersectedwith the long axis of the left ventricle at a plurality of time pointsin a cardiac cycle.

The motion of the myocardium can be deemed as the motion of endocardialcontour points or epicardial contour points. The motion of each contourpoint can influence the motion of a neighboring contour point.Therefore, the motion of an epicardial contour point can influence thatof a corresponding endocardial contour point, and vice verse. In themyocardial motion analysis method according to the embodiments of thepresent invention, a point linking pair is configured based on themotion correlation of an epicardial contour point and an endocardialcontour point, and the motion of the myocardium is represented with themotion of the point linking pair.

FIG. 14 is a schematic flow chart illustrating a myocardial motionanalysis method according to an embodiment of the present invention. Asshown in FIG. 14, in step S1410, an endocardial contour and anepicardial contour of a left ventricle are acquired in each image slice.The endocardial contour and the epicardial contour can be marked in eachimage slice manually or be acquired using any proper existing method. Asan example, the endocardial contour and the epicardial contour of theleft ventricle can be acquired using the moving object contour trackingmethod described in the part <1. Moving object contour tracking method>by taking the left ventricle as a moving object.

In step S1420, the contour points on the endocardial contour and theepicardial contour in a reference image slice of the image slice timeseries are configured as a plurality of point linking pairs, each pointlinking pair including a contour point on the endocardial contour and acontour point on the epicardial contour that are located on the samenormal of a reference contour of a left ventricle wall in the referenceimage slice. As an example, the reference contour may be the endocardialcontour, the epicardial contour or a mean contour acquired from theendocardial contour and the epicardial contour. That is, the linesegment defined by each point linking pair is located in asystolic/diastolic direction.

In order to facilitate understanding, FIG. 15 shows an example of apoint linking pair according to this embodiment. In order to facilitatedescription, a line segment defined by a point linking pair is referredto as a gauge.

In step S1430, the locations of each point linking pair in other imageslices of the image slice time series than the reference image slice aredetermined.

In step S1440, a motion vector of a myocardium of the left ventriclebetween adjacent image slices of the image slice time series iscalculated according to the locations of the plurality of point linkingpairs in the adjacent image slices, wherein the myocardium is defined bythe endocardial contour and the epicardial contour of the leftventricle.

Compared with existing myocardial motion analysis methods usingseparated contour points, the myocardial motion analysis methodaccording to the embodiment of the present invention adds constraints byrepresenting the motion of the myocardium with the motion of the pointlinking pairs, and therefore can analyze the motion of the myocardiummore stably.

In order to analyze the motion of the myocardium comprehensively,according to an embodiment of the present invention, a motion vector ofa myocardium between adjacent image slices is resolved into thefollowing motion components: systole/diastole, circumferentialexpansion/contraction of the myocardium of the left ventricle, rotationof the myocardium of the left ventricle, and twist of the myocardium ofthe left ventricle.

In order to facilitate understanding, FIG. 16 is a schematic diagramillustrating a myocardial motion component according to an embodiment ofthe present invention. In the case where the motion of a myocardium isrepresented with the motion of point linking pairs, the motion componentof systole/diastole can be represented with a component of the variationof the length of a line segment (gauge) defined by a point linking pairin a systole/diastole direction; the circumferentialexpansion/contraction of the myocardium can be represented by acomponent of the variation of the distance between two adjacent gaugesin the circumferential direction of the reference contour of the leftventricle; the rotation of the myocardium can be represented by acomponent of the movement (represented with an angle) of a gauge in thecircumferential direction of the reference contour of the leftventricle; and the twist of the myocardium can be represented by acomponent of the difference of the movements (each represented with anangle) of two contour points in a point linking pair in thecircumferential direction of the reference contour of the leftventricle.

Under the guide of the foregoing description, those skilled in the artcan calculate the respective motion components of the myocardium in anyway. A motion component calculation method according to an embodiment ofthe present invention is described below.

As an example, the motion component of systole/diastole may becalculated by calculating a difference of the projections of a linesegment defined by each point linking pair between adjacent imageslices, wherein the projections of the line segment are in a normaldirection of the reference contour in the reference image slice and thenormal direction passes through either of the contour points of thepoint linking pair.

As an example, the motion component of circumferentialexpansion/contraction of the myocardium of the left ventricle may becalculated by calculating a difference of projections of a distance of aline segment defined by a point linking pair to a line segment definedby an adjacent point linking pair between adjacent image slices, whereinthe projections of the distance are in a tangent direction of thereference contour in the reference image slice and the tangent directionpasses through the line segment defined by the point linking pair. As anexample but not a limitation, the distance may be a distance between themiddle point of the line segment defined by the point linking pair andthe middle point of the line segment defined by the adjacent pointlinking pair, or a length of a perpendicular line from either contourpoint of the point linking pair to the line segment defined by theadjacent point linking pair.

As an example, the motion component of rotation of the myocardium of theleft ventricle may be calculated by calculating a difference of anglesof a line segment defined by a point linking pair with respect to anormal direction of the reference contour in the reference image slicebetween adjacent image slices, wherein the normal direction passesthrough the line segment defined by the point linking pair. As anexample but not a limitation, the angle may be an angle of the linesegment defined by the point linking pair with respect to a normal ofthe reference contour in the reference image slice passing througheither contour point of the point linking pair or passing through themiddle point of the line segment defined by the point linking pair.

As another example, the image slice time series may be converted to apolar coordinate system by taking the center of the reference contour asa pole. The rotation of the myocardium between adjacent image slices maybe calculated using variation in an angle, which is presented in thepolar coordinate system, of the middle point of a line segment definedby each point linking pair or of either contour point of each pointlinking pair between adjacent image slices.

As an example, the motion component of twist of the myocardium of theleft ventricle may be calculated by calculating a difference of anglesof a normal direction of the reference contour in the reference imageslice passing through either contour point of each point linking pairand a normal direction of the reference contour in the reference imageslice passing through a middle point of a line segment defined by thepoint linking pair between adjacent image slices.

As another example, the image slice time series may be converted to apolar coordinate system by taking the center of the reference contour asa pole. The twist of the myocardium between adjacent image slices may becalculated according to a variation in an angle difference betweenadjacent image slices, wherein the angle difference is a differencebetween an angle of either contour point in each point linking pair inthe polar coordinate system and an angle of the middle point of a linesegment defined by the point linking pair in the polar coordinatesystem.

It should be appreciated that the locations of each point linking pairin other image slices in the image slice time series than thepredetermined image slice can be determined using any proper existingmethod. As an example, a method for determining the locations of eachpoint linking pair in the other image slices in the image slice timeseries according to an embodiment of the present invention is describedbelow.

While acquiring a contour of the moving object, the moving objectcontour tracking method according to the above embodiments also obtaincontinuous motion information of contour points of the moving object. Inone of the above embodiment, it is described that a weighted average ofthe motion vectors of tracking cells within a predetermined range andadjacent to each contour point of the contour of the moving object inthe current image slice can be calculated as a motion vector of thecontour point from the current image slice to the next image slice.Therefore, in an embodiment of the present invention, the location ofeach contour point in the next image slice may be determined using themotion vectors of the two contour points of a point linking pair fromthe current image slice to the next image slice, so as to determine thelocation of the point linking pair in the next image slice.

Specifically, the motion vector of a contour point on the endocardialcontour of the left ventricle in the current image slice from thecurrent image slice to the next image slice is calculated using themoving object contour tracking method according to the aboveembodiments, the left ventricle serving as a moving object; the locationof each endocardial contour point in the next image slice is acquiredbased on the motion vector of the endocardial contour point from thecurrent image slice to the next image slice; the motion vector of acontour point on the epicardial contour of the left ventricle in thecurrent image slice from the current image slice to the next image sliceis calculated using the moving object contour tracking method accordingto the above embodiments, the left ventricle serving as a moving object;the location of each epicardial contour point in the next image slice isacquired based on the motion vector of the epicardial contour point fromthe current image slice to the next image slice; and the location ofeach point linking pair in the next image slice is determined based onthe locations of each endocardial contour point and each epicardialcontour point in the next image slice.

In addition, as a heart is a moving entirety, the motion of themyocardium of the heart should be smooth. In an embodiment of thepresent invention, the respective motion components of the myocardiumare smoothed to provide a more accurate motion vector consisting of themotion components of the myocardium, and consequentially, a moreaccurate myocardial motion analysis is provided.

FIG. 17 is a schematic diagram illustrating the smoothing of a motioncomponent time series according to an embodiment of the presentinvention. As shown in FIG. 17, motion component time series, which areconstructed by the respective motion components of the motion vector ofthe myocardium of a left ventricle between adjacent image slices, aresmoothed. As an example but not a limitation, each motion component timeseries may be smoothed using a Fourier fitting method.

Accordingly, based on the endocardial contour and the epicardial contourof the left ventricle in the reference image slice, a new endocardialcontour and a new epicardial contour of the left ventricle in each otherimage slice of the image slice time series may be acquired by using thesmoothed motion component time series of the myocardium of the leftventricle between adjacent image slices, thereby providing a moreaccurate endocardial contour and epicardial contour.

In physics, strain refers to a relative deformation of an object underan external force. Myocardial strain means the deformation of amyocardium in a cardiac cycle, and can be used to evaluate the regionalmyocardial systolic and diastolic function and blood supply capabilityand the myocardial viability. After the motion vector of the myocardiumof the left ventricle is acquired using the myocardial motion analysismethod provided in the embodiments of the present invention, parametersof the myocardium of the left ventricle such as the myocardial strain,strain force and strain rate may be calculated according to the motionvector of the myocardium between adjacent image slices. There have beena number of existing methods for calculating the parameters such asmyocardial strain, strain force and strain rate according to the motionvector of the myocardium and these methods will not be described here indetail.

In order to present the strains of a myocardium intuitively, themyocardial motion analysis method according to an embodiment of thepresent invention further includes presenting the strains of themyocardium of the left ventricle on an image. FIG. 18 shows a view ofmyocardial strains according to an embodiment of the present invention.In this embodiment, there is a color bar at the left-upper side of theview. The different colors in the color bar correspond to differentmyocardial strains. According to this correspondence relationship, thecolors corresponding to the strains of different parts of the myocardiumcan be overlapped on the respective parts of the myocardium in an imageslice so that the doctor can see the strains of the myocardiumintuitively. In addition, a curve which shows the strain forces of amyocardium in the systole/diastole directions in a cardiac cycle isshown at the right-lower corner of the view. Under the guide of theforegoing description, those skilled in the art can devise moremyocardial strain presentation methods that will not be enumeratedherein.

<4. Myocardial Motion Analysis Method for a Three-Dimensional Image TimeSeries>

FIG. 19 is a schematic flow chart illustrating a myocardial motionanalysis method according to another embodiment of the presentinvention.

The myocardial motion analysis method according to the embodiment isused for analyzing the motion of the myocardium of a left ventricle in athree-dimensional medical image time series. The three-dimensionalmedical image time series includes a plurality of three-dimensionalimages that are acquired at a plurality of time points in a cardiaccycle. Each of the three-dimensional images consists of a plurality ofparallel two-dimensional image slices that are intersected with the longaxis of the left ventricle. The two-dimensional image slices located atthe same location in the three-dimensional images form an image slicetime series.

As shown in FIG. 19, in this method, in step S1910, the motion of themyocardium of the left ventricle is analyzed respectively in eachmedical image slice time series. Here, the motion of the myocardium ofthe left ventricle is analyzed in each medical image slice time seriesusing the myocardial motion analysis method described in the part <3.Myocardial motion analysis method>. The motions of the myocardium in theplurality of two-dimensional image slices at the same time point formthe motion of the left ventricle at this time point.

In addition, an image slice time series at a base part and an imageslice time series at an apex part may be recognized from thethree-dimensional medical image time series using any proper existingmethod. Then a myocardial motion analysis is only carried out on theimage slice time series in a range defined by the image slice timeseries at the base and the image slice time series at the apex.

<5. Moving Object Contour Tracking Apparatus>

A moving object contour tracking apparatus according to embodiments ofthe present invention is described below with reference to FIG. 20-FIG.26. The moving object contour tracking apparatus is configured to tracka contour of a moving object which deforms periodically in an imageslice time series. An image slice time series includes a plurality ofimage slices that are respectively acquired for the moving object at aplurality of time points in a motion period of the moving object. Itshould be appreciated that the moving object contour tracking apparatusaccording to the embodiments of the present invention can be used fortracking a contour of a moving object in various types of image slicetime series. As an example but not a limitation, the image slice timeseries may be a medical image series formed by examinee data obtainedthrough a medial diagnostic imaging device. The medial diagnostic deviceincludes but is not limited to an X-ray imaging diagnostic device, anultrasonic diagnostic imaging device, a computed tomography (CT) device,a magnetic resonance imaging (MRI) diagnostic device and a positronemission tomography (PET) device and the like.

FIG. 20 is a schematic block diagram illustrating a moving objectcontour tracking apparatus according to an embodiment of the presentinvention. As shown in FIG. 20, the moving object contour trackingapparatus 2000 includes a contour tracking section 2010, a contourcomparison section 2020 and a contour correction section 2030. Thecontour tracking section 2010 is configured to perform, by taking aninitial contour of the moving object in a predetermined image slice ofthe image slice time series as a starting contour, contour tracking inan image slice time series in a first time direction to acquire a firstcontour of the moving object in each image slice, wherein the last imageslice in the first time direction is taken as the previous image sliceof the first image slice; and to perform, by taking the initial contouras a starting contour, the contour tracking in the image slice timeseries in a second time direction to acquire a second contour of themoving object in each image slice, wherein the last image slice in thesecond time direction is taken as the previous image slice of the firstimage slice. The contour comparison section 2020 is configured tocalculate a similarity between the first contour of the moving object inthe predetermined image slice and the initial contour as a firstsimilarity, and a second similarity between the second contour of themoving object in the predetermined image slice and the initial contouras a second similarity. The contour correction section 2030 isconfigured to take the contours in the image slices tracked by thecontour tracking section 2010 in a contour tracking directioncorresponding to a greater one of the first and second similarities asthe contours of the moving object in the respective image slices.

In order to decrease the amount of calculation, according to anotherembodiment of the present invention, the contour tracking section 2010may perform a turn of contour tracking at first, that is, to acquire thecontour of the moving object in each image slice in one turn of contourtracking. The contour tracking section 2010 performs a second turn ofcontour tracking only when the contour comparison unit 2020 determines,based on the result of the first turn of contour tracking, that theremay be an error in the first turn of contour tracking. The contourcorrection section 2030 corrects the result of the first turn of contourtracking with the result of the second contour tracking. The specificimplementation mode may be understood by reference to relateddescription of the moving object contour tracking method as describedabove and is therefore not repeated here.

In the moving object contour tracking apparatus according to theembodiments of the present invention, the contour tracking section 2010may be realized using any proper existing method without limitation. Asan example, FIG. 21 shows a schematic block diagram illustrating acontour tracking section according to an embodiment of the presentinvention. As shown in FIG. 21, the contour tracking section 2100includes a region of interest (ROI) generation section 2110, a trackingcell division section 2120, a matching section 2130, a motion vectorcalculation section 2140 and a next contour determination section 2150.The ROI generation section 2110 is configured to expand the contour ofthe moving object in the current image slice to obtain a contour ROI.The tracking cell division section 2120 is configured to divide thecontour ROI into a plurality of tracking cells with a predeterminedsize. The matching section 2130 is configured to perform templatematching to obtain the locations of the plurality of tracking cells inthe next image slice. The motion vector calculation section 2140 isconfigured to calculate the motion vectors of the plurality of trackingcells from the current image slice to the next image slice according tothe locations of the plurality of tracking cells in the next imageslice. The next contour determination section 2150 is configured toacquire the contour of the moving object in the next image slice basedon the contour of the moving object in the current image slice and themotion vectors of the plurality of tracking cells from the current imageslice to the next image slice.

The motion vector calculation section 2140 can use any proper method tocalculate the motion vectors of the tracking cells. As a specificimplementation mode, the motion vector calculation section 2140 isconfigured to calculate a weighted average of the motion vectors of thetracking cells within a predetermined range and adjacent to each contourpoint on the contour of the moving object in the current image slice, asthe motion vector of the contour point from the current image slice tothe next image slice. Accordingly, the next contour determinationsection 2150 may be configured to move the contour of the moving objectin the current image slice according to the motion vector of eachcontour point on the contour of the moving object in the current imageslice so as to acquire the contour of the moving object in the nextimage slice.

In the moving object contour tracking apparatus according to theembodiments of the present invention, the initial contour of the movingobject in the predetermined image slice may be acquired in advance or beacquired by the moving object contour tracking apparatus. FIG. 22 is aschematic block diagram illustrating a moving object contour trackingapparatus according to another embodiment of the present invention. Inthis embodiment, the moving object contour tracking apparatus 2200includes an initial contour acquisition section 2240 for acquiring theinitial contour of the moving object in a predetermined image slice.

In this embodiment, the moving object is a left ventricle, the imageslice time series includes a plurality of image slices that are acquiredwith respect to a section of the left ventricle intersected with a longaxis of the left ventricle at a plurality of time points in a cardiaccycle. The left ventricle has an endocardial contour and an epicardialcontour. Therefore, the initial contour acquisition section 2240 may beconfigured to acquire an initial endocardial contour or an initialepicardial contour.

FIG. 23 is a schematic block diagram illustrating an initial contouracquisition section according to an embodiment of the present invention.As shown in FIG. 23, the initial contour acquisition section 2300includes a coordinate conversion section 2310 and an endocardial contouracquisition section 2320. The coordinate conversion section 2310 isconfigured to convert the predetermined image slice to a polarcoordinate system. The endocardial contour acquisition section 2320 isconfigured to acquire the endocardial contour of the left ventricle inthe polar coordinate system. The coordinate conversion section 2310 isfurther configured to map the endocardial contour acquired by theendocardial contour acquisition section 2320 in the polar coordinatesystem to the original predetermined image slice.

The endocardial contour acquisition section 2320 can acquire, in thepolar coordinate system, the endocardial contour of the left ventriclein the predetermined image slice using any proper existing method. As anexample, FIG. 24 is a schematic block diagram illustrating anendocardial contour acquisition section according to an embodiment ofthe present invention. In this embodiment, a rough location of theendocardial contour is determined in the polar coordinate system using ahorizontal projection of an image slice, and then the endocardialcontour is acquired from the edge image of the image slice using astraight line detection method. As shown in FIG. 24, the endocardialcontour acquisition section 2400 includes an edge detection section2410, a contour locating section 2420 and a contour fitting section2430. The edge detection section 2410 is used for detecting edges in thepredetermined image slice. The contour locating section 2420 is used foracquiring a radius of an endocardial contour of the left ventricle inthe polar coordinate system using a horizontal projection of a grayscale image of the predetermined image slice. The contour fittingsection 2430 is used for acquiring the endocardial contour of the leftventricle from the edges nearby the radius of the endocardial contourusing a straight line detection method. As an example but not alimitation, the straight line detection method is a Hough transformationmethod.

FIG. 25 is a schematic block diagram illustrating an initial contouracquisition section according to another embodiment of the presentinvention. As shown in FIG. 25, the initial contour acquisition section2500 includes a coordinate conversion section 2510 and an epicardialcontour acquisition section 2520. The coordinate conversion section 2510is configured to convert a predetermined image slice into a polarcoordinate system. The epicardial contour acquisition section 2520 isconfigured to acquire the epicardial contour of the left ventricle inthe polar coordinate system. The coordinate conversion section 2510 isfurther configured to map the epicardial contour acquired by theepicardial contour acquisition section 2520 in the polar coordinatesystem into the original predetermined image slice.

The epicardial contour acquisition section 2520 can acquire, in thepolar coordinate system, the epicardial contour of the left ventricle inthe predetermined image slice using any proper existing method. As anexample, FIG. 26 shows a schematic block diagram illustrating anepicardial contour acquisition section according to an embodiment of thepresent invention. As shown in FIG. 26, the epicardial contouracquisition section 2600 includes an edge detection section 2610, acontour locating section 2620 and a contour fitting section 2630. Theedge detection section 2610 is configured to detect edges in thepredetermined image slice. The contour locating section 2620 isconfigured to acquire, in the polar coordinate system, a radius of anendocardial contour of the left ventricle in the predetermined imageslice using a horizontal projection of a gray scale image of thepredetermined image slice, and to acquire a radius of an epicardialcontour of the left ventricle in the predetermined image slice using thehorizontal projection of an edge image of the predetermined image sliceand the radius of the endocardial contour of the left ventricle. Thecontour fitting section 2630 is configured to acquire, in the polarcoordinate system, the epicardial contour of the left ventricle fromedges nearby the radius of the epicardial contour of the left ventricleusing a curve fitting method. As an example but not a limitation, thecurve fitting method is a least square method.

In accordance with another embodiment of the present invention, themoving object contour tracking apparatus may further include aninterpolation determination section (not shown), which is configured todetermine whether the time interval spanned by the image slice timeseries is shorter than the motion period of the moving object, and aninterpolation execution section (not shown), which is configured tointerpolate a compensation image slice into the image slice time seriesif the time interval spanned by the image slice time series is shorterthan the motion period of the moving object, wherein the compensationimage slice is predicted using an image interpolation method.

More detailed operations related to each section in the moving objectcontour tracking apparatus can be understood by reference to thedescription on the moving object contour tracking method in the abovepart <1. Moving object contour tracking method> and therefore is notdescribed repeatedly here.

In the moving object contour tracking apparatus according to theembodiments of the present invention, the contour of the moving objectis tracked in two time directions, and the tracking result with a higherreliability is taken as the contour of the moving object, thus improvingthe accuracy of the contour tracking. In addition, in the case where themoving object is a left ventricle, the endocardial contour and theepicardial contour of the left ventricle may be acquired accurately byconverting the predetermined image slice to the polar coordinate system.

<6. Moving Object Contour Tracking Apparatus for a Three-DimensionalImage Time Series>

FIG. 27 is a schematic block diagram illustrating a moving objectcontour tracking apparatus according to another embodiment of thepresent invention.

The moving object contour tracking apparatus according to thisembodiment is configured to track the contour of a periodicallydeforming object in a three-dimensional image time series. Thethree-dimensional image time series includes a plurality ofthree-dimensional images that are acquired at a plurality of time pointsin a motion period of the moving object. Each of the three-dimensionalimages consists of a plurality of parallel two-dimensional image slices.The two-dimensional image slices located at the same location in theplurality of three-dimensional images form an image slice time series.

As shown in FIG. 27, the moving object contour tracking apparatus 2700includes a tracking section 2710. The tracking section 2710 isconfigured to track the contour of the moving object in each image slicetime series. Here, the tracking section 2710 may be implemented by themoving object contour tracking apparatus described in the above part <5.Moving object contour tracking apparatus>. The contours of the movingobject in the plurality of two-dimensional image slices at the same timepoint form a three-dimensional contour of the moving object at this timepoint.

In addition, the moving object contour tracking apparatus 2700 mayfurther include a control section (not shown), which inputs the imageslice time series in the three-dimensional image time series into thetracking section 2710 one by one.

In addition, the moving object contour tracking apparatus 2700 mayfurther include a limitation location recognizing device (not shown) forrecognizing the image slice time series respectively corresponding tothe two ends of the moving object from the three-dimensional image timeseries.

<7. Myocardial Motion Analysis Apparatus>

The myocardial motion analysis apparatus provided in embodiments of thepresent invention is described below with reference to FIG. 28-FIG. 31.The myocardial motion analysis apparatus is used for analyzing themotion of a myocardium of a left ventricle in a medical image slice timeseries. The image slice time series includes a plurality of image slicesthat are acquired with respect to a section of the left ventricleintersected with the long axis of the left ventricle at a plurality oftime points in a cardiac cycle. In the myocardial motion analysisapparatus according to the embodiments of the present invention, a pointlinking pair is configured based on the motion correlation of anepicardial contour point and an endocardial contour point, and themotion of the myocardium is represented with the motion of the pointlinking pair.

FIG. 28 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to an embodiment of the present invention.As shown in FIG. 28, the myocardial motion analysis apparatus 2800includes a contour acquisition section 2810, a point linking pairconfiguration section 2820, a point linking pair tracking section 2830and a motion vector calculation section 2840.

In this embodiment, the contour acquisition section 2810 is configuredto acquire the endocardial contour and the epicardial contour of theleft ventricle in each image slice. The point linking pair configurationsection 2820 is configured to configure the contour points on theendocardial contour and the epicardial contour in a reference imageslice of the image slice time series as a plurality of point linkingpairs, each point linking pair including a contour point on theendocardial contour and a contour point on the epicardial contour, andtwo contour points of each point linking pair being located on the samenormal of a reference contour of a wall of the left ventricle in thereference image slice. The point linking pair tracking section 2830 isconfigured to determine the locations of each point linking pair inother image slices of the image slice time series than the predeterminedimage slice. The motion vector calculation section 2840 is configured tocalculate, according to the locations of the plurality of point linkingpairs in adjacent image slices of the image slice time series, a motionvector of a myocardium of the left ventricle between the adjacent imageslices, wherein the myocardium is defined by the endocardial contour andthe epicardial contour.

As an example, the reference contour may be the endocardial contour, theepicardial contour or a mean contour acquired from the endocardialcontour and the epicardial contour.

According to another embodiment of the present invention, the motionvector calculation section 2840 is further configured to calculate thefollowing motion components of the motion vector of the myocardium ofthe left ventricle between adjacent image slices: systole/diastole,circumferential expansion/contraction of the myocardium of the leftventricle, rotation of the myocardium of the left ventricle, and twistof the myocardium of the left ventricle. Specifically, the motion vectorcalculation section 2840 may calculate the aforementioned motioncomponents using the motion component calculation method described inthe part <3. Myocardial motion analysis method>.

The contour acquisition section 2810 can receive an endocardial contourand an epicardial contour that are manually marked in each image sliceor acquire an endocardial contour and an epicardial contour using anyproper existing method. As an example, the contour acquisition section2810 can be implemented by the moving object contour tracking apparatusaccording to an embodiment of the present invention to acquire theendocardial contour and the epicardial contour of the left ventricle bytaking the left ventricle as a moving object.

While acquiring the contour of the moving object, the moving objectcontour tracking apparatus according to the above embodiments alsoobtain continuous motion information of contour points of the movingobject. According to another embodiment of the present invention, in thecase where the contour acquisition section 2810 is implemented by themoving object contour tracking apparatus according to an embodiment ofthe present invention, the point linking pair tracking section 2830 isfurther configured to acquire the location of each endocardial contourpoint of the left ventricle in the next image slice based on the motionvector of the endocardial contour point from the current image slice tothe next image slice, the left ventricle serving as a moving object; toacquire the location of each epicardial contour point of the leftventricle in the next image slice based on the motion vector of theepicardial contour point of the left ventricle in the current imageslice from the current image slice to the next image slice, wherein theleft ventricle serves as a moving object, and the motion vector of theepicardial contour point of the left ventricle is calculated by themotion vector calculation section 2140 of the moving object contourtracking apparatus; and to acquire the location of each point linkingpair in the next image slice based on the locations of each endocardialcontour point and each epicardial contour point in the next image slice.

Of course, the point linking pair tracking section 2830 may be directlyimplemented by the moving object contour tracking apparatus according toan embodiment of the present invention, and calculate the location ofeach endocardial contour point and the location of each epicardialcontour point in the next image slice based on the motion vectors of theendocardial contour point and the epicardial contour point so as todetermine the location of each point linking pair in the next imageslice.

In an embodiment of the present invention, the respective motioncomponents of the myocardium are smoothed to provide a more accuratemotion vector consisting of the motion components of the myocardium, andconsequentially, a more accurate myocardial motion analysis is provided.FIG. 29 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to another embodiment of the presentinvention. As shown in FIG. 29, the myocardial motion analysis apparatus2900 includes a contour acquisition section 2910, a point linking pairconfiguration section 2920, a point linking pair tracking section 2930,a motion vector calculation section 2940 and a smoothing section 2950.The contour acquisition section 2910, the point linking pairconfiguration section 2920, the point linking pair tracking section 2930and the motion vector calculation section 2940 are respectivelyidentical to the contour acquisition section 2810, the point linkingpair configuration section 2820, the point linking pair tracking section2830 and the motion vector calculation section 2840 shown in FIG. 28 instructure and function. The smoothing section 2950 is configured tosmooth motion component time series which are constructed by therespective motion components of the motion vector of the myocardium ofthe left ventricle between adjacent image slices.

FIG. 30 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to another embodiment of the presentinvention. In this embodiment, the myocardial motion analysis apparatus3000 includes a contour acquisition section 3010, a point linking pairconfiguration section 3020, a point linking pair tracking section 3030,a motion vector calculation section 3040 and a smoothing section 3050,which are respectively identical to the contour acquisition section2910, the point linking pair configuration section 2920, the pointlinking pair tracking section 2930, the motion vector calculationsection 2940 and the smoothing section 2950 shown in FIG. 29 instructure and function. In addition, the myocardial motion analysisapparatus 3000 further includes a contour optimization section 3060,which is configured to acquire, based on the endocardial contour and theepicardial contour of the left ventricle in a reference image slice, anew endocardial contour and a new epicardial contour of the leftventricle in each of the other image slices of the image slice timeseries by using the smoothed motion component time series of themyocardium of the left ventricle between adjacent image slices, therebyproviding a more accurate endocardial contour and epicardial contour.

FIG. 31 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to another embodiment of the presentinvention. In this embodiment, in addition to including a contouracquisition section 3110, a point linking pair configuration section3120, a point linking pair tracking section 3130 and a motion vectorcalculation section 3140 which are identical to those in the myocardialmotion analysis apparatus shown in FIG. 28, the myocardial motionanalysis apparatus 3100 further includes a parameter calculation section3170 and a presentation section 3180. The parameter calculation section3170 is configured to calculate a strain of the myocardium of the leftventricle according to the motion vector of the myocardium of the leftventricle between adjacent image slices. The presentation section 3180is configured to present the strain of the myocardium of the leftventricle on a corresponding original image slice.

In addition, preferably, the myocardial motion analysis apparatus 3100may further include a smoothing section 3150 and/or a contouroptimization section 3160. The smoothing section 3150 is identical tothe smoothing section 2950 shown in FIG. 29 in structure and function.

More detailed operations related to each section in the myocardialmotion analysis apparatus can be understood by reference to thedescription given in the part <3. Myocardial motion analysis method> onthe myocardial motion analysis method, and is therefore not describedrepeatedly here.

The myocardial motion analysis apparatus according to the embodiments ofthe present invention adds constraints by representing the motion of themyocardium with the motion of the point linking pairs, and therefore cananalyze the motion of the myocardium more stably. In addition, themotion of the myocardium can be comprehensively analyzed by resolvingthe motion vector of the myocardium into motion components such as thesystole/diastole, the circumferential expansion/contraction, therotation and the twist. In addition, the motion components of themyocardium are smoothed to provide a more accurate motion vectorconsisting of the motion components of the myocardium, thereby providinga more accurate myocardial motion analysis. The endocardial contour andthe epicardial contour are re-acquired based on the smoothed motionvector, and thus the re-acquired contours are more accurate.

<8. Myocardial Motion Analysis Apparatus for a Three-Dimensional MedicalImage Time Series>

FIG. 32 is a schematic block diagram illustrating a myocardial motionanalysis apparatus according to a further embodiment of the presentinvention.

The myocardial motion analysis apparatus according to this embodiment isused for analyzing the motion of the myocardium of a left ventricle in athree-dimensional medical image time series. The three-dimensionalmedical image time series includes a plurality of three-dimensionalimages that are acquired at a plurality of time points in a cardiaccycle. Each of the three-dimensional images consists of a plurality ofparallel two-dimensional image slices that are intersected with the longaxis of the left ventricle. The two-dimensional image slices located atthe same location in the three-dimensional images form an image slicetime series.

As shown in FIG. 32, the myocardial motion analysis apparatus 3200includes an analysis section 3210, which is configured to analyze themotion of the myocardium of the left ventricle in each medical imageslice time series. Here, the analysis section 3210 may be implemented bythe myocardial motion analysis apparatus described in the part <7.Myocardial motion analysis apparatus>. The motions of the myocardium inthe plurality of two-dimensional image slices at the same time pointform a motion of the left ventricle at this time point.

In addition, the myocardial motion analysis apparatus 3200 may include acontrol section (not shown), which inputs the image slice time series inthe three-dimensional medical image time series into the analysissection 3210 one by one.

In addition, the myocardial motion analysis apparatus 3200 may furtherinclude a limitation location recognizing device (not shown), which isconfigured to recognize the image slice time series at a base part andthe image slice time series at an apex part from the three-dimensionalmedical image time series.

<9. Computer Structure Capable of Implementing the Methods/ApparatusesDisclosed in the Embodiments of the Present Invention>

As an example, the respective steps of the above-described moving objectcontour tracking method and myocardial motion analysis method and therespective sections, modules and/or units of the above-described movingobject contour tracking apparatus and myocardial motion analysisapparatus may be implemented as software, firmware, hardware or thecombination thereof in a medical diagnostic apparatus (e.g. X-raydiagnostic device, UL diagnostic device, CT device, MRI diagnosticdevice or PET device), and serve as a part of the medical diagnosticapparatus. As an example, the above-described methods and/or apparatusesmay be implemented in an existing medical diagnostic device by makingsome modification on the sections of the existing medical diagnosticdevice. As another example, the respective steps of the above-describedmethods and the respective sections, modules and/or units of theabove-described apparatuses may be implemented as an apparatusseparately from the above-described medical diagnostic apparatus. Thespecific means or approaches that may be used in configuring thesections, modules and units in the foregoing apparatuses throughsoftware, firmware, hardware or any combination thereof are well knownto those skilled in the art and therefore will not be repeatedlydescribed.

As an example, the steps of the above-described methods and thesections, modules and/or units of the above-described apparatuses may beimplemented as software, firmware, hardware or any combination thereof.In the case where the steps of the above-described methods and thesections, modules and/or units of the above-described apparatuses areimplemented through software or firmware, a software programconstituting the software for realizing the above-described methods maybe installed in a computer (e.g. the general computer 3300 shown in FIG.33) with a specific hardware structure from a storage medium or anetwork, and the computer, when installed with various programs, iscapable of perform various functions.

In FIG. 33, a central processing unit (CPU) 3301 executes variousprocesses according to the programs stored in a read-only memory (ROM)3302 or programs loaded to a random access memory (RAM) 3303 from astorage part 3308. Data needed by the CPU 3301 to execute the variousprocesses are also stored in the RAM 3303 as required. The CPU 3301, theROM 3302 and the RAM 3303 are connected with each other via a bus 3304.An input/output interface 3305 is also connected to the bus 3304.

The following parts are connected to the input/output (I/O) interface3305: an input part 3306 (including a keyboard, a mouse and etc.), anoutput part 3307 (including a display such as a cathode-ray tube (CRT)or a liquid crystal display (LCD), and a speaker, etc.), the storagepart 3308 (including a hard disk, etc.), and a communication part 3309(including a network interface card such as an LAN card, a MODEM andetc.). The communication part 3309 executes communication processing viaa network such as the Internet. A driver 3310 can also be connected tothe input/output interface 3305 as required. A removable medium 3311such as a magnetic disk, an optical disk, a magneto-optical disk or asemiconductor memory can be mounted on the driver 3310 as required, suchthat the computer program read out therefrom is installed into thestorage part 3308 as required.

In the case that the above series of processes are implemented bysoftware, a program constituting the software is installed from anetwork such as the Internet or from a storage medium such as theremovable medium 3311.

It is to be understood by those skilled in the art that such storagemedium is not limited to the removable medium 3311 storing programstherein and distributing the programs to a user(s) dependently from adevice. Examples of the removable medium 3311 include a magnetic disk(including a Floppy Disk (FD) (registered trademark)), an optical disk(including a Compact Disk-Read Only Memory (CD-ROM) and a DigitalVersatile Disc (DVD)), a magneto-optical disk (including a Microdisk(MD) (registered trademark)) and a semiconductor memory. Alternatively,the storage medium can be the ROM 3302, a hard disk contained in thestorage part 3308, etc., in which programs are stored and which isdistributed to a user(s) along with a device the storage medium iscontained in.

The present invention further provides a program product in whichcomputer-readable instruction codes are stored. The instruction codes,when read and executed by a machine, can execute the methods accordingto the embodiments of the present invention.

Correspondingly, the storage medium for carrying the program productstoring machine-readable instruction codes is also incorporated in thedisclosure of the present invention. The storage medium includes, but isnot limited to, a flexible disk, an optical disk, a magneto-opticaldisk, a storage card and a storage stick.

In the above description of the specific embodiments of the presentinvention, features described and/or illustrated with respect to oneembodiment can be used in one or more other embodiments in an identicalor similar manner, be combined with features in other embodiments, orreplace features in other embodiments.

It should be emphasized that, the term “comprise/include”, as used inthe present description, refers to the presence of features, sections,steps or components, but does not exclude the presence or addition ofone or more other features, sections, steps or components.

In the above embodiments and examples, the steps and/or units arerepresented with a reference sign consisting of numbers. It should beunderstood by those of ordinary skill of the art that the referencesigns are merely intended to facilitate description and drawingdepiction, but are not to be construed as indicating the orders of thesteps and/or units nor a limitation on any other aspect.

Furthermore, the methods of the present invention are not limited tobeing executed in the temporal orders as described in the specification,but can also be executed in other temporal order, in parallel orseparately. Therefore, the execution orders of the methods described inthe present specification do not constitute limitation to the technicalscope of the present invention.

Although the present invention has been disclosed with reference todescriptions for the specific embodiments of the present invention, itshould be understood that all of the above mentioned embodiments andexamples are illustrative instead of limiting. Those skilled in the artcan devise various modifications, improvements or equivalents for thepresent invention, within the spirit and scope of the appended claims.The modifications, improvements or equivalents should also be consideredas being included in the protection scope of the present invention.

What is claimed is:
 1. A myocardial motion analysis apparatus foranalyzing a motion of a myocardium of a left ventricle in a medicalimage slice time series, the medical image slice time series comprisinga plurality of image slices acquired with respect to a section of theleft ventricle intersected with a long axis of the left ventricle at aplurality of time points in a cardiac cycle, the apparatus comprising: acontour acquisition section configured to acquire an endocardial contourand an epicardial contour of the left ventricle in each image slice; apoint linking pair configuration section configured to configure contourpoints on the endocardial contour and the epicardial contour in areference image slice of the image slice time series as a plurality ofpoint linking pairs, each point linking pair comprising a contour pointon the endocardial contour and a contour point on the epicardialcontour, and the two contour points of each point linking pair beinglocated on the same normal of a reference contour of a left ventriclewall in the reference image slice; a point linking pair tracking sectionconfigured to determine locations of each point linking pair in otherimage slices of the image slice time series; and a motion vectorcalculation section configured to calculate, according to the locationsof the plurality of point linking pairs in adjacent image slices of theimage slice time series, a motion vector of the myocardium of the leftventricle between the adjacent image slices, the myocardium beingdefined by the endocardial contour and the epicardial contour.
 2. Theapparatus according to claim 1, wherein the motion vector calculationsection is further configured to calculate the following motioncomponents of the motion vector of the myocardium of the left ventriclebetween the adjacent image slices: systole/diastole, circumferentialexpansion/contraction of the myocardium of the left ventricle, rotationof the myocardium of the left ventricle, and twist of the myocardium ofthe left ventricle.
 3. The apparatus according to claim 2, wherein themotion vector calculation section is further configured to calculate adifference of projections of a line segment defined by each pointlinking pair between adjacent image slices as the motion component ofsystole/diastole, wherein the projections of the line segment are in anormal direction of the reference contour in the reference image sliceand the normal direction passes through either of the contour points ofthe point linking pair.
 4. The apparatus according to claim 2, whereinthe motion vector calculation section is further configured to calculatea difference of projections of a distance of a line segment defined byeach point linking pair to a line segment defined by an adjacent pointlinking pair of the point linking pair between adjacent image slices asthe motion component of circumferential expansion/contraction of themyocardium of the left ventricle, wherein the projections of thedistance are in a tangent direction of the reference contour in thereference image slice and the tangent direction passes through the linesegment defined by the point linking pair.
 5. The apparatus according toclaim 2, wherein the motion vector calculation section is furtherconfigured to calculate a difference of angles of a line segment definedby each point linking pair with respect to a normal direction of thereference contour in the reference image slice between adjacent imageslices as the motion component of rotation of the myocardium of the leftventricle, wherein the normal direction passes through the line segmentdefined by the point linking pair.
 6. The apparatus according to claim2, wherein the motion vector calculation section is further configuredto calculate a difference of angles of a normal direction of thereference contour in the reference image slice passing through eithercontour point of each point linking pair and a normal direction of thereference contour in the reference image slice passing through a middlepoint of a line segment defined by the point linking pair betweenadjacent image slices, as the motion component of twist of themyocardium of the left ventricle.
 7. The apparatus according to claim 1,wherein the reference contour of the left ventricle wall in thereference image slice is the endocardial contour, the epicardial contouror a mean contour acquired from the endocardial contour and theepicardial contour.
 8. The apparatus according to claim 1, wherein thepoint linking pair tracking section is further configured to: acquire alocation of each endocardial contour point of a left ventricle servingas a moving object in the next image slice based on a motion vector ofan endocardial contour point from the current image slice to the nextimage slice, acquire a location of each epicardial contour point of theleft ventricle serving as a moving object in the next image slice basedon a motion vector of an epicardial contour point of the left ventriclein the current image slice from the current image slice to the nextimage slice, and determine the location of each point linking pair inthe next image slice based on the locations of each endocardial contourpoint and each epicardial contour point in the next image slice.
 9. Theapparatus according to claim 2, further comprising a smoothing sectionconfigured to smooth a motion component time series constructed by eachmotion component of the motion vector of the myocardium of the leftventricle between adjacent image slices.
 10. The apparatus according toclaim 9, further comprising a contour optimization section configured toacquire, based on the endocardial contour and the epicardial contour ofthe left ventricle in the reference image slice, a new endocardialcontour and a new epicardial contour of the left ventricle in each ofthe other image slices of the image slice time series using the smoothedmotion component time series of the myocardium of the left ventriclebetween adjacent image slices.
 11. The apparatus according to claim 1,further comprising: a parameter calculation section configured tocalculate a strain of the myocardium of the left ventricle according tothe motion vector of the myocardium of the left ventricle betweenadjacent image slices; and a presentation section configured to presentthe strain of the myocardium of the left ventricle on a correspondingoriginal image slice.
 12. The apparatus according to claim 1, whereinthe contour acquisition section is further configured to: track anendocardial contour of a left ventricle serving as a moving object inthe image slice time series to acquire the endocardial contour of theleft ventricle in each image slice, and track an epicardial contour ofthe left ventricle serving as a moving object in the image slice timeseries to acquire the epicardial contour of the left ventricle in eachimage slice.
 13. A myocardial motion analysis apparatus for analyzing amotion of a myocardium of a left ventricle in a three-dimensionalmedical image time series, the three-dimensional medical image timeseries comprising a plurality of three-dimensional images acquired at aplurality of time points in a cardiac cycle, each of thethree-dimensional images consisting of a plurality of paralleltwo-dimensional image slices that are intersected with a long axis ofthe left ventricle, and the two-dimensional image slices located at thesame location in the three-dimensional images forming an image slicetime series, the apparatus comprising: an analysis section implementedby the myocardial motion analysis apparatus according to claim 1, andconfigured to analyze the motion of the myocardium of the left ventriclein each medical image slice time series, wherein the motions of themyocardium in the plurality of two-dimensional image slices at the sametime point form a motion of the left ventricle at this time point.
 14. Amyocardial motion analysis method for analyzing a motion of a myocardiumof a left ventricle in a medical image slice time series, the medicalimage slice time series comprising a plurality of image slices acquiredwith respect to a section of the left ventricle intersected with a longaxis of the left ventricle at a plurality of time points in a cardiaccycle, the method comprising: acquiring an endocardial contour and anepicardial contour of the left ventricle in each image slice;configuring contour points on the endocardial contour and the epicardialcontour in a reference image slice of the image slice time series as aplurality of point linking pairs, each point linking pair comprising acontour point on the endocardial contour and a contour point on theepicardial contour, and the two contour pints of each point linking pairbeing located on the same normal of a reference contour of a leftventricle wall in the reference image slice; determining locations ofeach point linking pair in other image slices of the image slice timeseries; and calculating, according to the locations of the plurality ofpoint linking pairs in adjacent image slices of the image slice timeseries, a motion vector of the myocardium of the left ventricle betweenthe adjacent image slices, the myocardium being defined by theendocardial contour and the epicardial contour.